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Terrestrial Planet Interiors Applying what we have learned about Earth’s interior to other planets tells us what their interiors are probably like.

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Why do water and oil separate? A.Water molecules repel oil molecules electrically. B.Water is denser than oil, so oil floats on water. C.Oil is more slippery than water, so it slides to the surface of the water. D.Oil molecules are bigger than the spaces between water molecules.

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Why do water and oil separate? A.Water molecules repel oil molecules electrically. B.Water is denser than oil, so oil floats on water. C.Oil is more slippery than water, so it slides to the surface of the water. D.Oil molecules are bigger than the spaces between water molecules.

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Thought Question What is necessary for differentiation to occur in a planet? A.It must have metal and rock in it. B.It must be a mix of materials of different density. C.Material inside must be able to flow. D.All of the above. E.b and c.

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Thought Question What is necessary for differentiation to occur in a planet? A.It must have metal and rock in it. B.It must be a mix of materials of different density. C.Material inside must be able to flow. D.All of the above. E.b and c.

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Lithosphere A planet’s outer layer of cool, rigid rock is called the lithosphere. It “floats” on the warmer, softer rock that lies beneath.

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Thought Question Do rocks s-t-r-e-t-c-h? A.No—rock is rigid and cannot deform without breaking. B.Yes—but only if it is molten rock. C.Yes—rock under strain may slowly deform.

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Thought Question Do rocks s-t-r-e-t-c-h? A.No—rock is rigid and cannot deform without breaking. B.Yes—but only if it is molten rock. C.Yes—rock under strain may slowly deform.

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Strength of Rock Rock stretches when pulled slowly but breaks when pulled rapidly. The gravity of a large world pulls slowly on its rocky content, shaping the world into a sphere.

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Role of Size Smaller worlds cool off faster and harden earlier. Moon and Mercury are now geologically “dead.”

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Surface Area to Volume Ratio Heat content depends on volume. Loss of heat through radiation depends on surface area. Time to cool depends on surface area divided by volume: Larger objects have a smaller ratio and cool more slowly.

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Thought Question If the planet core is cold, do you expect it to have magnetic fields? A.Yes, refrigerator magnets are cold, and they have magnetic fields. B.No, planetary magnetic fields are generated by moving charges around, and if the core is cold, nothing is moving.

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Thought Question If the planet core is cold, do you expect it to have magnetic fields? A.Yes, refrigerator magnets are cold, and they have magnetic fields. B.No, planetary magnetic fields are generated by moving charges around, and if the core is cold, nothing is moving.

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Special Topic: How do we know what’s inside a planet? P waves push matter back and forth. S waves shake matter side to side.

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Special Topic: How do we know what’s inside a planet? P waves go through Earth’s core, but S waves do not. We conclude that Earth’s core must have a liquid outer layer.

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Impact Cratering Most cratering happened soon after the solar system formed. Craters are about 10 times wider than objects that made them. Small craters greatly outnumber large ones. The Production of a Crater

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Outgassing Volcanism also releases gases from Earth’s interior into the atmosphere.

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Tectonics Convection of the mantle creates stresses in the crust called tectonic forces. Compression forces make mountain ranges. A valley can form where the crust is pulled apart. Tectonics and Convection of the Mantle

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A Greenhouse Gas Any gas that absorbs infrared Greenhouse gas: molecules with two different types of elements (CO 2, H 2 O, CH 4 ) Not a greenhouse gas: molecules with one or two atoms of the same element (O 2, N 2 )

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Greenhouse Effect: Bad? The Earth is much warmer because of the greenhouse effect than it would be without an atmosphere…but so is Venus.

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Erosion on Venus Photos of rocks taken by lander show little erosion

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Does Venus have plate tectonics? Most of Earth’s major geological features can be attributed to plate tectonics, which gradually remakes Earth’s surface. Venus does not appear to have plate tectonics, but its entire surface seems to have been “repaved” 750 million years ago.

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Thought Question What is the main reason why Venus is hotter than Earth? A.Venus is closer to the Sun than Earth. B.Venus is more reflective than Earth. C.Venus is less reflective than Earth. D.The greenhouse effect is much stronger on Venus than on Earth. E.Human activity has led to declining temperatures on Earth.

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Thought Question What is the main reason why Venus is hotter than Earth? A.Venus is closer to the Sun than Earth. B.Venus is more reflective than Earth. C.Venus is less reflective than Earth. D.The greenhouse effect is much stronger on Venus than on Earth. E.Human activity has led to declining temperatures on Earth.

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What unique features of Earth are important for life? 1.Surface liquid water 2.Atmospheric oxygen 3.Plate tectonics 4.Climate stability

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What unique features of Earth are important to human life? 1.Surface liquid water 2.Atmospheric oxygen 3.Plate tectonics 4.Climate stability Earth’s distance from the Sun and moderate greenhouse effect make liquid water possible.

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What unique features of Earth are important to human life? 1.Surface liquid water 2.Atmospheric oxygen 3.Plate tectonics 4.Climate stability PHOTOSYNTHESIS (plant life) is required to make high concentrations of O 2, which produces the protective layer of O 3.

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What unique features of Earth are important to human life? 1.Surface liquid water 2.Atmospheric oxygen 3.Plate tectonics 4.Climate stability Plate tectonics are an important step in the carbon dioxide cycle.

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What unique features of Earth are important to human life? 1.Surface liquid water 2.Atmospheric oxygen 3.Plate tectonics 4.Climate stability The CO 2 cycle acts like a thermostat for Earth’s temperature.

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These unique features are intertwined: Plate tectonics create climate stability Climate stability allows liquid water Liquid water is necessary for life Life is necessary for atmospheric oxygen How many other connections between these can you think of?

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Dangers of Human Activity Human-made CFCs in the atmosphere destroy ozone, reducing protection from UV radiation. Human activity is driving many other species to extinction. Human use of fossil fuels produces greenhouse gases that can cause global warming.

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Global Warming Earth’s average temperature has increased by 0.5°C in the past 50 years. The concentration of CO 2 is rising rapidly. An unchecked rise in greenhouse gases will eventually lead to global warming.

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CO 2 Concentration Global temperatures have tracked CO 2 concentration for the last 500,000 years. Antarctic air bubbles indicate the current CO 2 concentration is at its highest level in at least 500,000 years.

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CO 2 Concentration Most of the CO 2 increase has happened in last 50 years!

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Modeling of Climate Change Complex models of global warming suggest that the recent temperature increase is indeed consistent with human production of greenhouse gases.

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What makes a planet habitable? Located at an optimal distance from the Sun for liquid water to exist

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What makes a planet habitable? Large enough for geological activity to release and retain water and atmosphere

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Planetary Destiny Earth is habitable because it is large enough to remain geologically active, and it is at the right distance from the Sun so oceans could form.